齊藤 敦53Atsushi SAITO和達 大樹54Hiroki WADATI光励起誘電率増加効果を利用した超高速チューナブルフィルタの開発 (2014年採択)Development of high-speed tunable filer using enhancing permittivity by optical excitation (Project 2014)軟X線カー効果による遷移金属酸化物薄膜の磁性研究と時間分解測定への応用 (2015年採択)Studying magnetism of transition-metal-oxide thin films by soft x-ray Kerr effects and their application to time-resolved measurements (Project 2015)47次世代情報通信技術の進展のため，通信帯域を瞬時に切り替え可能な超高速チューナブルフィルタが必要とされている．本研究の最終目的は光励起誘電率増加効果を利用した超高速チューナブルフィルタの開発である．本報告では光照射による高周波帯域での比誘電率の変化を評価可能な測定系を構築し，SrTiO3 の光照射特性を調査した．その結果，1〜100 MHz 帯での光励起誘電率増加効果を初めて確認することができた．High-speed tunable filter which can be changed frequency band is required for the development of the next-generation information network system. The final goal of our study is development of the high-speed tunable filter using enhancing permittivity by optical excitation. In this report, we developed the measure-ment system for the variation of the permittivity in high-frequency region by optical irradiation and investi-gated the optical properties of SrTiO3. Thereby, we first found that the enhancing permittivity by optical ex-citation in the range from 1 MHz to 100 MHz.直線偏光したX線を用いて元素選択的な強磁性シグナルを得る手法として，軟X線カー効果測定の確立を行った．偏光制御可能なアンジュレーターを用い，FeのL端でFeナノ薄膜の軟X線カー効果測定を行った．入射X線がs偏光とp偏光の両方の場合にL3，L2端で大きなカー回転角を得た．さらに，自由電子レーザー施設FERMIを用い，時間分解軟X線カー効果測定を行うことで，フェリ磁性合金GdFe-Coの超高速磁化反転の観測も行った．GdFeCo合金を赤外レーザーパルスでポンプした後，GdFeCoのFeの磁化の時間発展を，自由電子レーザーパルスのエネルギーをFeのM端にすることで，元素選択的に観測した．We established soft x-ray Kerr effect measurments to obtain element-specific ferromagnetic signals by using linearly polarized x-ray. We performed the measurements of soft x-ray Kerr effects of an Fe nanofilm at the Fe L-edge using the polarization controlled undulator. We obtained large values of the Kerr rotation angle at the L3 and L2 absorption edges for both of s- and p-polarized incident lights. We also observed ultrafast mag-netization reversal of a ferrimagnetic metallic alloy GdFeCo by time-resolved soft x-ray Kerr effect measure-ments using a free electron laser facility FERMI. After pumping the GdFeCo alloy by an infrared laser pulse, the following temporal evolution of the magnetization of Fe in GdFeCo was element-selectively traced by a free electron laser pulse with a photon energy tuned to the Fe M-edge.
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